Lift mechanism with low oil control



Jan. 16, 1968 1. v. K. HOTT ETAL LIFT MECHANISM WITHLOW OIL CONTROL Filed Oct. 20, 1965 m m mwm w WWW wzwv mw flw /M7 0V 6 United States Patent 3,363,511 LIFT MECHANISM WITH LOW OIL CONTROL Ion V. K. Hott and David M. Goldzwig, Dayton, Ohio, assignors to The Joyce-Cridland Company, Dayton, Ohio, a corporation of Ohio Filed Oct. 20, 1965, Ser. No. 498,386 4 Claims. (Cl. 91-4) ABSTRACT OF THE DISCLOSURE Two valve members are positioned within the hollow piston of a semi-hydraulic lift. One of the valve members is a float which seats under low oil conditions. The other valve member surrounds the air tube and stops the flow of oil through the aperture in the piston base plate surrounding the air tube. The latter valve member includes an O-ring seal encircling the air tube and biased out of sealing engagement therewith. The increase in pressure resulting from the seating of the float overcomes the bias and causes the O-ring to seal against the air tube.

This invention relates to a lift and more particularly to a device for controlling the operation of a semi-hydraulic vehicle lift when an inadequate level of liquid is present in the lift piston or ram. As will be apparent, the invention is not necessarily so limited. For convenience, and because oil is usually used in vehicle lift installations, the term oil used herein is intended to refer to any viscous liquid which may be used in vehicle lifting apparatus.

In United States Patent No. 2,763,128, issued to Ion V. K. Hott on Sept. 18, 1956, a low oil control device is disclosed involving the use of a magnesium float guided in a perforated tube located in an oil reservoir. If the oil level in the reservoir becomes dangerously low, the float engages a valve seat at the base of the tube and cuts off the oil flow from the reservoir. This principle has been applied to the type of lift known as semi-hydraulic wherein an air tube extends from the base of the lift cylinder and through most of the lift piston as illustrated in United States Patent No. 3,179,014, issued to Ion V. K. Hott and David M. Goldzwig on Apr. 20, 1965. In the latter patent, the air tube was used as a guide for a float assembly having a pair of floats for balance. In addition to the structure shown in the aforementioned patents, another low oil control system was used for a brief period of time in which a perforated tube, such as shown in the aforesaid Patent No. 2,763,128, was mounted in the piston of a semi-hydraulic lift and extended upwardly from a fluid passageway in the piston base plate spaced from the aperture through which the air tube extended. The aperture for the air tube was sealed by a plurality of seal plates connected to the piston base plate. This system was only partially successful because no satisfactory permanent annular seal between the piston base plate and the air tube was developed. A permanent connection or seal between the air tube and the piston base plate was found undesirable because of damage caused to the air tube, the seal or both.

An object of this invention is to provide an improved low oil control device especially adapted for use with semi-hydraulic lifts.

Another object of this invention is to provide an improved low oil control device for semi-hydraulic lifts in which two fluid passageways between the lift piston and the lift cylinder are sequentially closed.

Still another object of this invention is to provide an improved pressure responsive annular seal. More specifically, it is an object of this invention to seal against fluid or air flow between a piston base plate and an air tube in a semi-hydraulic lift, but only under low oil conditions.

3,363,511 Patented Jan. 16, 1968 Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

Referring to the drawings:

FIGURE 1 is a cross-sectional view of a portion of a semi-hydraulic lift provided with a low oil control apparatus made in accordance with this invention.

FIGURE 2 is an enlarged cross-sectional view of a valve or sealing device taken as indicated by the arrows 22 of FIGURE 1.

With reference to FIGURE 1, this invention is illustrated in a lift mechanism including a lift cylinder 10 having a cylinder base plate 12 in which is slidably mounted a lift piston or ram 14 having a piston base plate 16 and a piston top plate 18. The piston 14 is guided within the cylinder 10 by a bearing structure including an upper bearing ring 20 and a lower bearing ring 22 which are connected by a bearing sleeve 24. This bearing assembly is supported by a threaded connection between the lower bearing ring 22 and a bearing support ring 26 welded internally of the cylinder 10. The lowermost position of the piston 14, which is that position illustrated in FIGURE 1, is determined by engagement of the bottom of the casing forming the piston 14 with the top surface of the cylinder base plate 12. Upward movement of the piston 14 within the cylinder 10 may be limited by an enlarged annular flange 28 at the base of the piston 14 which strikes the bottom of the lower bearing ring 22 at the extreme upper limit of travel.

The piston 14 and the cylinder ltl are normally substantially filled with oil. To confine the oil within the cylinder 14), a plurality of packing rings 31) are supported by the top surface of the upper bearing ring 20. The packing rings 30 are held in position by a packing gland ring 32 clamped, as by a plurality of bolts 34, to a cylinder bolt ring 36 which in turn is welded to the cylinder 10. As usual in constructions of this type, the packing gland ring 32 may be provided with a groove for retaining a resilient wiper ring 38, which serves to wipe the outer surface of the piston 14- as it lowers, and a lubricating groove 4t Afiixed as by welding internally of the top of the piston 14 above the piston top plate 18 is a piston bolt ring 42 provided with a plurality of bolt receiving apertures. As well known, the bolt ring 42 is used in atfixing a vehicle engaging superstructure (not shown) to .the top of the piston 14.

When initially installed, the piston 14 and the cylinder 11 are substantially filled with oil introduced into the piston 14 through a fill port 44 located in a plate 46 and fitted into a sleeve 48 which is integral with the piston top plate 18. The fill port 44 is normally closed by a plug 50 threaded therein to which is attached an oil level dip stick 52 which should occasionally be removed for guaging the oil level within the piston 14. Oil entering through the port 44 can flow from the piston 14 into the cylinder 10 through a central aperture 54 surrounding an air tube 56 which extends centrally through the piston 14 and derives support from a support fixture 58 mounted centrally of the cylinder base plate 12. Oil also flows through a fluid metering passageway 60 located in the piston base plate 16 in spaced relation to the aperture 54. Because there cannot be a perfect fit between the bottom of the piston 14 and the top surface of the piston base plate 16, oil will flow around the bottom of the piston 14 into the surrounding area between the piston 14 and the cylinder 10. In FIGURE 1, a slot 62 is illustrated in the lower bearing ring 22. This bearing ring 22 may be constructed with a plurality of bearing pads, designated 64, similar to that illustrated in United States Patent No. 3,186,312, granted on June 1, 1965, to Ion V. K. Hott and Robert J.

Haddix. Oil and air can therefore enter into the gap between the piston .14 and the bearing sleeve 24. To avoid undesirable trapping of air, a plurality of small ports, designated 66, are located in the top of the hearing assembly, either at the top of the bearing sleeve 2 or in the bottom of the upper bearing 20. Air can thus escape from within the sleeve 24 to the exterior of the sleeve 24 and through a conventional air bleeder valve 63.

After the piston 14 and cylinder have been filled with oil, the piston 14 can be elevated by introduction of air under pressure from a suitable compressed air source (not shown) into an air inlet tube 76 in the bottom of the cylinder 10. Air under pressure follows the passageway through the inlet tube 70 and the air tube 56 to the top of the lift piston 14 and coacts between the top of the oil within the piston 14 and the piston top plate 13 to cause the piston 14- to rise. As the piston 14 rises, the aperture 54 surrounding the air tube 56 is almost immediately substantially closed by an apertured upper seal plate 72 encircling the air tube 56 and connected to or integral with a hollow seal plate sleeve 74 which also encircles the air tube 56. When the piston 14 is in the lowered position shown in FIGURE 1, the bottom of the seal plate 72 abuts the top of the support fixture 58, thereby holding the seal plate 72 above the piston base plate 16. However, when the piston 14 rises, the relatively large annular bottom face of the seal plate 72 seats against the top surface of the piston base plate 16 surrounding the aperture 54. As described more fully below, practically no oil normally flows through the sleeve 74 about the air tube 56. Hence, the speed of ascent of the piston 14 is therefore controlled primarily by the rate of fluid flow through the fluid metering passageway 69.

After the piston has been elevated to the desired height, an air valve (not shown) in the air line leading to the air inlet tube 70 is closed. To avoid entrainment of air in the oil, an air baflle plate 76 is welded internally of the piston 14 beneath the piston top plate 1-8. Because of its length and the fact that the piston 14 and cylinder 10 will normally be shipped in a horizontal position, the air tube 56 is provided with a shipping protector 78 having a plurality of guide arms 80 which engage the margins of a central aperture 82 in the baffle plate 76 during shipment. After installation, the guide arms 80 serve to recenter the air tube 56 each time the piston 14 lowers from an elevated position.

Pressurized air confined within the cavity in the piston 14 above the oil level will reasonably maintain the elevated position of the piston, especially since assisted by the dampening effect of the oil in the cylinder 10 and the lower part of the piston 14. When it is desired to lower the piston 14, the aforementioned air valve in the air line leading to the air tube 56 is opened to exhaust air from the piston 14 through the tube 56 to atmosphere. Gravity will then cause the piston 14 to lower, again under the control provided by the limited rate of fluid flow permitted through the fluid passageway 69. The aperture 54 surrounding the air tube 56 again will be closed during lowering, at this time by a lower seal plate 84 which is also mounted on the seal plate sleeve 74 and afiixed thereto in any suitable manner (not shown).

The structure as thus far described may operate satisfactorily throughout its useful life, especially if the oil level within the piston is periodically checked by removal and inspection of the dip stick 52 and if an adequate oil level is maintained. Occasionally, due to faulty maintenance, leakage, or other causes, the oil level within the piston 14 becomes so low that, unless the rise of piston 14- is stopped, its base plate 16 rises above the top of the oil. This low oil condition can be quite dangerous since the control provided by metering of oil through the fluid passageway 60 is lost. That is, air under pressure will uncontrollably rush into the cylinder 10 through the passageway 60. As a result, the piston 14 will rise erratically. When fully elevated, it will not be supported in oil and will tend to float clue to the unstable support provided by the compressed air.

Subsequently, upon lowering the piston 14, there will be no control over the initial descent thereof until it again lowers into the oil.

As has previously been done, means are provided to close the fluid passageway 60 in the event such low oil conditions occur. This means is illustrated herein in the form of a hollow, lightweight meta-l float of the type described in the aforesaid Hott Patent No. 2,763,128, confined for movement within a perforated tube 92 supported at its upper end within another aperture 94 in the baffle plate '76 and mounted at its lower end in an opening 98 in a hollow support member 96 which may be integral with or fixedly mounted on the piston base plate 16. The support member 96 overlies and serves as an extension of the passageway 60. Oil may therefore flow from the perforated tube 92 through the fluid passageway 60 thus extended into the cylinder 10. A generally conical valve seat 199 is cut in the passageway 98 and cooperates with the semispherical base of the float 90 to close the passageway 60 if the level of oil within the piston 14 should become dangerously low. To confine the float 90 within the perforated tube 92, the dip stick 52 extends into the top of the perforated tube 92 and is provided with a small disc-shaped abutment 102 at its lower end. As illustrated, a hook 104 may be amxed to the top of the float 90 so that it may easily be grasped by a simple tool for removal and inspection.

As mentioned above, the seal plates 72 and 84 ride with the piston base plate 16 as it rises and lowers. The pr'mary purpose of the seal plates 72 and 84 is to avoid a tight fit between the aperture 54 within the piston base plate 16 and the air tube 56. if a tight fit were used at that point, the piston base plate 16 likely would bind on, or at least cause considerable damage to, the air tube 56 because the air tube 56 will not always be truly vertcal and the aperture 54 not always be precisely centrally located. Similarly, there must be a loose fit between the internal diameter of the hollow seal plate sleeve 74 and the air tube 56 so that, upon rising and lowering of the piston 14, the sleeve 74 will not cause damage to the air tube 56.

Because of the loose fit between the seal plate sleeve 74 and the air tube 56, some of the oil within the piston 14 and cylinder 10 will flow through the aperture in the seal plate sleeve '74. Normally this fiow will be minimal because of the much larger flow through the passageway 60. However, in the event of a low oil condition resutt ng in closure of the fluid passageway 60, an extremely large pressure differential will exist in the lift mechanism between the piston 14 and the cylinder 10. Unless sealed, oil and ultimately air would flow through the aperture in the seal plate sleeve 74, around the air tube 56. In accordance with this invention, such flow of fluid around the air tube 56 is prevented by a further sealing device or valve means, generally designated 106, which rests upon and moves with the upper seal plate 72.

With reference to FIGURE 2, the sealing device or valve means 1% is shown as comprising a generally cylindrical housing 108 having a central bore 11% extending therethrough which encircles the air tube 56. The housing 108 has a planar housing base surface 112. of sufiicient area to create a satisfactory seal with the top surface of the upper seal plate 72. A hollow housing sleeve is formed within the housing 108 and, as illustrated, includes a fixed upper hollow sleeve element 114 having an annular tapered bottom surface aligned with a slidable, lower hollow sleeve element 116 having an annular tapered top surface. The tapered surfaces of the sleeve elements 114 and 116 are confronting and generally parallel. To hold the upper sleeve element 114 in a fixed position, its upper end is enlarged and confined between a sleeve support ledge 118 formed near the top of the bore 110 and a spring retainer ring 120 lodged in a groove in the housing 108 and of conventional design. An annular cavity 122 is formed between the confronting tapered surfaces of the two sleeve elements 116 and 118 and houses an elastomeric O-ring sealing member 124 encircling the the air tube 56. The O-ring 124 has an internal diameter larger than the external diameter of the air tube 56. The lower sleeve element 116 is biased upwardly within the bore 110 by a coil spring 126 coiled about the air tube 56 and confined within the bore 110, which for this purpose is of reduced diameter at its lower end.

The fit between the sleeve internally of the housing 108 formed by the sleeve elements 114 and 116 about the air tube 56 is a loose fit, again to prevent binding of the sealing device 106 against the air tube 56 or damage to the air tube 56. Because biased upwardly by the spring 126 acting upon the lower sleeve element 116 and because of its larger diameter, the internal margins of the O-ring 124 normally only loosely fit around the air tube 56, and in fact, may not engage the air tube 56. A plurality of small passageways 128 in the housing 108 extend downwardly from the exterior of the housing 108 to the annular cavity 122 in which the O-ring sealing member 124 is located. If the high pressure conditions previously described resulting from closure of the fluid metering passageway 60 under low oil conditions occurs, the lower sleeve element 116 will be forced downwardly by oil in the passageways 128 against the bias of the spring 126 and, at the same time, the O-rir1g 124 will be pressed downwardly fully into engagement with the air tube 56. Thus, a fluid and air tight seal will be formed between the upper tapered surface of the lower sleeve element 116 and the adjacent annular surface of the air tube 56.

From the foregoing, it is seen that an improved low oil control device has been provided involving the sequential closing of, first, the passageway 60 and then the aperture about the air tube 56 through the seal plate sleeve 74. It will be noted that the effective closing of the passageway 60 occurs at the opening 98 in the particular embodiment shown in the drawing. This construction was desired to insure that the float 90 would seat before the piston 14 was raised so high that air could enter the small passageways 128 in the housing 108. Thus, there is no danger of air passing from the piston 14 into the cylinder 10.

The effect of a low oil condition existing in a lift incorporating the float 90 and the sealing device 106 is to completely stop continued rise of the piston 14. As well known, excess pressure build-up within the piston 14 is avoided by conventional relief valve means (not shown) at the air compressor or in the air line leading to the air tube 56. Although continued rise of the lift piston 14 is prevented, it can be lowered as if no low oil condition existed. That is, air within the piston 14 is exhausted to atmosphere, resulting in a pressure differential caused by gravity acting upwardly upon the float 90, the movable sleeve element 116 and the O-ring 124. Even if insufllcient to raise the float 90 because of an inadequate oil level within the piston 14, the pressure differential added to the bias of the coil spring 126 will cause the seal around the air tube 56 to break, whereupon oil from the cylinder will re-enter the piston 14. Ultimately, the oil level within the piston 14 will be sufficient to cause the float 90 to rise above the valve seat 100. Lowering of the piston 14 will then continue as already discussed above.

Although the presently preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation,

which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described our invention, we claim:

1. A lift mechanism including a hollow piston slidably mounted within a cylinder, said piston and said cylinder being substantially filled with oil, said piston having a piston base plate with a fluid passageway therein providing fluid communication between said piston and said cylinder, a tube projecting upwardly through a surrounding aperture in said piston base plate, said tube enabling the introduction of air under pressure above the top level of oil within said piston thereby raising said piston relative to said cylinder, and sequentially operating valve means closing said fluid passageway and said surrounding aperture in response to the oil within said piston approaching a level so low as to otherwise permit air to pass through said fluid passageway and said surrounding aperture.

2. In a lift mechanism of the type wherein a hollow piston is slidably mounted within a cylinder, said piston and said cylinder being substantially filled with oil, said piston having a base plate with a fluid passageway therein providing fluid communication between said piston and said cylinder, said piston being raised relative to said cylinder by the introduction of air under pressure above the top level of oil within said piston through a tube projecting upwardly through a surrounding aperture in said piston base plate, sequentially operating valve means closing said fluid passageway and said surrounding aperture comprising: a buoyant valve member adapted to float in the oil within said piston, a valve seat fixed in relation to said fluid passageway, said buoyant valve member engaging said valve seat and closing sa d fluid passageway whenever the oil within said piston falls to a predetermined low level, and sealing means responsive to a pressure differential created upon closure of said fluid passageway between the inside and outside of said piston preventing the passage of liquid through said surrounding aperture.

3. The structure of claim 2 wherein said sealing means comprises a housing supported by said piston base plate, said housing having a hollow sleeve through which said tube passes, and a sealing member in said housing simultaneously engaging an exterior surface portion of said tube and an annular surface portion of said hollow sleeve upon creation of said pressure differential within said piston by closure of said fluid passageway.

4. The structure of claim 3 wherein said sleeve includes a fixed sleeve element mounted in said housing, a movable sleeve element aligned with said fixed sleeve element and slidable in said housing about said tube, said sealing member comprising an elastomeric O-ring encircling said tube and confined between said sleeve elements, and wherein means within said housing biases said movable sleeve element toward said fixed sleeve element.

References Cited UNITED STATES PATENTS 2,402,265 6/ 1946 Thompson 91-4 2,637,302 5/1953 Harrison et al. 91-4 2,970,577 2/1961 Sinclair 91-4 3,140,641 7/1964 Clark et al. 91-4 3,203,317 8/1965 Taylor 91-4 3,237,523 3/1966 Wallace 91-4 FOREIGN PATENTS 705,438 9/1930 France.

EDGAR W. GEOGHEGAN, Primary Examiner. P. E. MASLOUSKY, Assistant Examiner. 

